This section is intended to introduce the reader to various aspects of art which may be related to various aspects of the present invention which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Manufacturers of wireless communication devices have a wide range of transmission technologies to choose from when designing wireless systems. Some exemplary technologies include time division multiple access (“TDMA”), code division multiple access and the like. CDMA, which is typically implemented using direct sequence spread spectrum technology, is very popular in communications systems, including cellular telephones and the like.
In a CDMA system, a code or symbol is assigned to all speech bits in a voice signal. The symbols are encoded across a frequency spectrum and transmitted to a receiver. When the encoded CDMA symbols are received, they are decoded and reassembled into a signal representative of the original voice signal.
In processing received CDMA signals, it may be difficult to detect long symbols in the presence of a frequency offset. Because the chips (each chip is equal to one bit in a spreading code) that make up a symbol may tend to rotate in the presence of a frequency offset, it is possible for the chips to rotate completely around the complex plane during the integration period of one symbol. When this happens, the chips may destructively combine to produce a very small correlation peak. One method may be to solve this problem may be to implement a frequency synchronization block in hardware, but such solutions may be undesirably expensive in order to be able to tolerate higher frequency offsets. Absent more expensive hardware solutions, a receiver may only be able to detect long symbols in the presence of relatively low frequency offsets. An improved method and apparatus for the detection of long symbols in the presence of a relatively high frequency offset is desirable.